1. Field of the Invention
The present invention relates to a method of driving a ring spinning frame, more particularly, it relates to a method of controlling the driving of a ring spinning frame wherein spindles are driven at a very high rotation speed.
2. Description of the Related Art
In the method of driving a ring spinning frame, it is well known that the rotation speed of spindles is controlled by a control program whereby, during the driving operation for producing a full packaged cop of yarn by each ring-spindle winding unit of the ring spinning frame, the rotation speed of each spindle is increased from the starting of the driving operation until the bottom tapered portion of a cop is formed. At this point, the rotation speed of each spindle reaches the maximum speed thereof, and the driving speed of each spindle is maintained until the yarn volume of the cop of each spindle become 90% of the full packaged cop, and thereafter the driving speed of each spindle is lowered to zero and the production of the full packaged cops by the ring spinning frame is completed. The main purpose of driving the spindles of a ring spinning frame according to the above-mentioned program control method is to prevent possible yarn breakages during the period of forming the above-mentioned bottom tapered portion and of forming a top tapered portion of each full packaged cop, as disclosed in Japanese Unexamined Patent Publication Sho No. 61 (1986) 201,028, and Japanese Unexamined U.M. Publication Sho No. 63 (1988) 64,781.
Currently, since the accuracy of machined elements has become very high due to the remarkable developments in machine tools, it is easy to obtain machine elements related to the ring-spindle mechanism that have a high machine accuracy and high quality, and accordingly, it is possible to increase the driving speed of the spindles to a high level of more than 25,000 rpm, which is remarkably higher than the driving speed of spindles of conventional ring spinning frames. Such a high speed driving of spindles causes several serious problems, such as an excessive vibration of the machine elements, and the creation of loud noise, etc., but such problems have been solved by modern technology. Nevertheless, although a skilled person in the art recognizes the above-mentioned problems related to the high speed driving of the ring spinning frame, there is no recognition of more serious problems such as an acceptable variation of yarn count. Accordingly, the above-mentioned program control method of regulating the rotation speed of spindles has been only applied to modernize the spinning operation.
Under the above general situation it was found that, when the rotation speed of spindles of a ring spinning frame reaches more than a certain limit, such as 26,000 rpm, the thickness of yarn produced under such a driving condition of the spindle becomes thinner than the expected thickness, (hereinafter referred to as "loss of yarn thickness") as recognized after repeated tests, and it is obvious that the above change of the yarn thickness cannot be neglected, from the viewpoint of quality control. Accordingly, the purpose of the present invention is to practically solve the above serious problem from the viewpoint of quality control.